The present invention relates to an ultrasonic washing apparatus having a sound pressure sensor for detecting an ultrasonic wave for washing generated by an ultrasonic vibrator.
In a prior ultrasonic washing apparatus, a housing has a central hollow portion and an inclined hollow portion, A nozzle is formed at the end of the inclined portion, and a step portion is formed in the central hollow portion. An ultrasonic vibrator is mounted on the step portion, A high frequency oscillator is connected to the ultrasonic vibrator through connected lines, and a liquid flowing inlet is connected to the central hollow portion of the housing and to a liquid supply means.
When a liquid as a washing liquid is supplied to the housing by the liquid supply means and the oscillating output from the high frequency oscillator is applied to the ultrasonic vibrator, liquid with ultrasonic waves flows from the nozzle of the housing, and a surface of an object such as a semiconductor placed in the front of the nozzle is washed by the liquid and ultrasonic waves.
In this ultrasonic washing apparatus, since a sound pressure sensor is large, the sound pressure sensor must be placed at the position of the object for detecting the ultrasonic waves in the liquid flowing from the nozzle of the housing, and the voltage detected by. the sound pressure sensor is measured by a voltmeter.
Therefore, the ultrasonic waves in the liquid cannot be detected by the sound pressure sensor when the object is washed.